Sheet separating and feeding apparatus

Abstract

A sheet feeding device adapted to separate a single sheet from a stack of sheets and forward the separated sheet away from the stack for subsequent processing. The apparatus includes a feed belt mounted for movement on at least two stationary rolls and a movable roll, the section of the belt between the two stationary rolls being adapted for frictional engagement with retard means forming a sheet feed nip therebetween. A sheet sensor adjacent the retard means and the feed belt is employed to displace the movable roll and the portion of the feed belt mounted thereon into engagement with the sheet stack to increase the feed belt "foot print" when the absence of a sheet is sensed during a feed cycle to increase the feed force on the sheet. The feed mechanism is adapted to operate on the bottom sheet of a sheet stack which is subjected to a flow of pressurized air against the bottom sheet to reduce friction between the bottom sheet and the stack tray and between the bottom sheet and the sheet immediately thereabove.

What is claimed is: 
     
       1. An apparatus for feeding and separating individual sheets from a stack of sheets including: a first feed roll mounted on a stationary axis adjacent the forward edge of the stack for separating sheets from the stack under normal operating conditions;   a second feed roll mounted on a second axis adjacent said first feed roll, said second axis being movable toward and away from the stack to move said second feed roll toward and away from the stack;   friction surface means associated with said first roll and said second roll, movement of said second roll toward the stack causing an increase in the friction surface area contacting the stack; and,   means for automatically moving said second roll toward said stack when a non-feed condition is encountered during a sheet feed cycle.   
     
     
       2. An apparatus for feeding and separating individual sheets from a stack of sheets including: an endless sheet feeding and separating belt mounted for sheet feeding engagement with the edge of the stack of sheets, said belt being rotatably mounted on a plurality of rolls, a first one of said rolls being disposed adjacent the edge of the stack to support said belt in contact with the stack, a second one of said rolls being disposed adjacent said first roll, the axis of said second roll being movable toward and away from the stack to force a greater portion of said belt into contact with the stack when said second roll is moved toward the stack,   a stationaty retard pad mounted opposite said belt between said first roll and a third one of said rolls, said third roll being disposed on the side of said first roll opposite said second roll, said stationary retard pad being located to depress said belt between said first and third rolls, said belt being formed of a substantially non-stretch material, movement of said second roll toward said stack causing increased tension on said belt to increase the force between said belt and said stationary retard pad to increase the retard action therebetween; and,   means for moving said second roll toward said stack when a non-feed condition is encountered during a sheet feed cycle.   
     
     
       3. A sheet feeding and separating apparatus according to claim 1 wherein said friction means comprises an endless belt rotatably mounted on said first and second rolls, movement of said second roll toward the stack forcing a greater portion of said belt into contact with the stack when a non-feed condition is encountered during a sheet feed cycle. 
     
     
       4. A sheet feeding and separating apparatus according to claim 3 further including a third roll, said third roll being adapted to rotatably support said belt on the side of said first roll opposite said second roll; and, a stationary retard pad mounted on the side of said belt opposite said rolls between said first roll and said third roll, said stationary retard pad causing said belt to be depressed between said first and third rolls, said belt being formed of a substantially non-stretch material;   means mounting said second roll for movement in a direction toward said stack away from said first and third rolls, movement of said second roll toward said stack causing increased tension on said belt to increase the force between said belt and said stationary retard pad to increase the retard action therebetween.   
     
     
       5. A sheet feeding and separating apparatus according to claim 2 further including belt tensioning means to maintain a predetermined tension on said belt; means mounting said second roll for movement toward said stack, away from said first and third rolls, the length of the belt path around said first, second, and third rolls when said second roll is moved toward said stack being greater than the length of said belt when said belt is under said predetermined tension, movement of said second roll toward the stack thereby causing a tension on said belt in excess of the tension maintained thereon by said tensioning means.   
     
     
       6. A sheet feeding and separating apparatus according to claim 2 further including perforated tray means adapted to support the stack of sheets thereon said sheet feeding and separating belt being mounted adjacent said tray to feed sheets individually from the bottom of the stack; and, means for supplying air under pressure through the perforations in said tray to reduce the frictional force between the bottom sheet of the stack and the tray.   
     
     
       7. A sheet feeding and separating apparatus according to claim 6 wherein said perforated sheet tray includes upstanding sides thereon adapted for engagement with the edges of the sheets in the stack, air escaping from between said tray and the lowest sheet in the stack being forced between said upstanding sides and the edges of the sheets in the stack, a portion of the air passing thereby being forced between adjacent sheets near the bottom of the stack to reduce the friction between the bottom sheet in the stack and the sheet immediately thereabove. 
     
     
       8. A sheet feeding and separating apparatus according to claim 1 further including sheet sensing means disposed downstream from said first feed roll, said sheet sensing means being adapted to activate said means for moving said second roll toward said stack when the absence of a sheet is sensed by said sensing means at a predetermined point in the sheet feed cycle.